A good detective story, as with the classic Conan Doyle writings, has all the clues to solve the crime in front of the reader. Only the writing is so good that to solve it the reader has to be as good as the detective in question, as good as the great Sherlock Holmes.
If it all works, once Holmes reveals the killer at the end of the story, it becomes THE SIXTH SENSE ending-kind-of-moment. The reader is not only awestruck, not only chiding him/herself that they missed it, but feels delight that it all fits. They replay the story in their minds and realize that the clues were always there, they just didn't put it together.
In this episode, the emails that led to the killer's reveal, we weren't privy to. They were discovered, read, and deductions made thereof behind the scenes almost incidental. It was as if Sherlock and Watson had a theory, then sort and found the evidence to prove it, without our witnessing it.
They didn't find the damning clues first, then deduced the killer from them. As a result, the feeling that the viewer , as with the reader of the classic Sherlock tales, of competing with the great detective to find the killer, by putting it all together first, is missing.
When evidence is withheld from the viewer, for Sherlock to use in his big reveal at the end, surprising both the killer and the viewer, is cheating by the writers.
Moreover, ELEMENTARY, then falls in danger of becoming a clone of THE MENTALIST series. Jane, like Holmes, is an astute man, observant of human nature and able to see things as no other around him can. Yet in his own show, we see very little deductive reasoning from Jane. Often it is as if he guessed who the killer is, then concocted some gimmick to get the killer to reveal him/herself , the gimmick itself aimed to work on no other but the hitherto hidden killer.
In each case, Jane then had some fore-knowledge of the killer for him to come up with the gimmick, but how he came to his conclusions, to this knowledge, the viewer is not shown.
We don't really see how Jane's brain works. THE MENTALIST writers go to pains to make Jane appear smart, but they do it by not revealing anything to the audience until the last minute.
With Holmes, he is supposed to appear smart because nothing is hidden to the audience, but he is able to interpret it all beyond the capabilities of the audience.
And even then, once he reveals his conclusions, reveals the killer, every audience member should have the same response as the other characters/other observers around Holmes, the response of realization, of "of course!", followed by a figurative smack to the forehead.
This is what a real Sherlock Holmes story should be.
On another note, given Watson's new status, I've waited 18 episode before making up my mind, now have to comment: I don't like that Watson is female. In the Sherlock Holmes stories, Watson is not only Holmes biographer (which Joan doesn't even consider here), he is Holmes' confidant, his springboard for ideas, his friend, his doctor, the only one (except to some degree Mrs. Hudson, Holmes' housekeeper whom is sorely missed in this show) who really sees the real Sherlock Holmes. Watson is the only person in front of whom Holmes will let his hair down, whom he will allow to see his vulnerabilities. Watson is the only person Holmes trusts without question, and as such, the only person who is able to keep Holmes grounded.
Holmes is Sheldon from THE BIG BANG THOERY, without the comedy, who is so clinical he is unable to relate to other humans or their emotions. Watson keeps Holmes human, and stops him from falling into an impersonal world of cold facts and emotionless relationships.
Joan and Sherlock won't be able to reach this level of intimacy without the show wandering into the territory of all other TV dramas that have a male and female lead, the old fallback of sexual tensions the-will-they-won't-they? senerio, if you will- to keep another level of audience interest.
Please, god-like writers, Sherlock and Watson should never become lovers, nor should there ever ever be any hint of it. But how then, can you portray the closeness as outlined above, which would be easier to do if the characters were both male, and seemingly impossible when one is female, without implying sexual tension or sexual interest?